Epoxy question

chevytrucking said:
Man, you guys are making nervous. I was literally going to glue my scales on tonight with Loctite 5 minute epoxy. I'm using 3 Corby's and my stabilized scales are sanded dead nuts flat, so I figured the epoxy would be more of a super thin layer of sealer than a fastener. If the handle is rock solid mechanically, is this even much of an issue?
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With three corbys you should be fine with the moisture sealant of locate. To me it just makes sense to use the best available. I just prefer to use the G-flex or Acraglass like Ed has mentioned because they both will have better long term results.
 
I say go for it chevy, just make sure all the mating surfaces are roughed up good and cleaned with acetone. everybody here is going to have differing opinions on epoxy just like lots of other steps in making knives. it's up to you to decide what you think is the best process in your knife making, but I don't think knives are falling apart all across the U.S. or we would certainly be hearing more of the products that prove to be inferior.
that said.. be careful using the 5 min. stuff. you better make sure you have all your ducks in a row, cause when it starts setting up there ain't no stopping it !
 
Its MORE than just opinions, It 20-30 plus years of individual experience. We use to use the 5 min epoxy and stopped using it for the reason that 5 minute can mean that the knife can come back in five years or so with separating scales.

I'm in this for the long haul and get referrals from people that I made knives for 5-10-15 years ago and plan on keeping it that way!
 
Actually these are just opinions, from different knife makers and their experience with different epoxies. I haven't seen any scientific stuff here on epoxies so there just opinions, just like mine. I have knives out there that I made twenty five years ago that show no delamination of the scales, and there not sitting in safes, there being used. sorry if I ruffled some feathers, but I'm in this for the long haul too, and I haven't had any of the problems that were mentioned here. so why should I change the way I do things ?
 
One of the things I remember learning back in the olden days from Tracey's Glue Wars, is that whatever epoxy you are using, it needs to be mixed more than you think it does. IIRC, the advice was to mix twice as long as you figured or the instructions said. I've done so, just because so many experienced makers agreed with that advice.

Rob!
 
From many many years of epoxy work, even back in polyester days, the really big important thing to completely degrease both surfaces and leave a good mechanical bite to surface. I normally leave a 36 grit finish to provide a good "bite". While epoxy resins have some adhesive ability, the mechanical bond is also very important. Polyester resins have almost no adhesive strength but rely primarily on the mechanical bond.

On the epoxy break downs over the years - not sure what epoxy has suffered from this, but in many years of boat work with polyester and epoxy resins, I've never seen that problem. The 40 ft sailboat I lived on for over 25 yrs was a polyester resin boat built in 1964 and that hull was very strong, and it had many epoxy resin repairs done over the years. I just liked using epoxy better than polyester. Epoxy resin had the reputation of being stronger than polyester n the boating world.

Any of the epoxy or polyester resins will break down in sun light from the UV, so some covering MUCH be applied over resin to protect from sunshine. This "most epoxy breaks down in a manner of years" is completely new to me, except ALL will break down in sunshine.

I don't know much about this "fast cure" stuff, nor much about the small tubes of epoxy from racks in stores, I'm only referring to epoxies used in boating world.

Ken H>
"Just an old boat bum"
 
All good stuff to know.

So those of you who have had knives returned, what do you do? It is possible to re-set the scales?

I'd imagine in the least it would require at least a little refinishing of the handle material and tang. But how bad does it get? If the epoxy has come loose and the handles are loose enough while still pinned, have you had to scrap any handles because the pins aren't holding anymore?

I ask this, because I've always just assumed the epoxy was more of a sealant than what was actually holding the scale on the tang...even if it was only pinned. Usually with only pins while I'm fitting everything, there's a pretty tight hold already.
 
I have three hidden tang knives in my shop drawer from when I first started making hidden tangs on my own. They were practice knives and fortunately, never went to a customer.

I still use them to practice different techniques on. All of them were glued with 5 min two part devcon epoxy. Two of them have pins one does not.

All of them were filled with epoxy so that it oozed out around the guard when I put the tangs in. Two of them I drilled a tiny hole in the handle to let air out (which did nothing that I can tell besides contribute to the mess and left a small hole besides).

All three of them now can twist side to side in the handle and all of them, when held in one hand and shaken lightly, will definitely rattle around inside the handle. All of them are less than three years old.

I have another hidden tang knife that I made at another maker's shop that is at least 4 years old, maybe 5. We used g flex epoxy with NO PINS and I have literally beat the snot out of that knife in the woods and it shows no sign of twisting, rattling or anything coming loose at all.

Those are my experiences. Call it an opinion or whatever you want but it is good enough proof for me.
 
The single biggest surprise, for me, that came out of the glue wars testing I did back then was:

A marginal glue with a great surface preparation will out perform a great glue with poor surface preparation.

When manufactures test bonding on adhesives, they use standard metal coupons (something like mild steel in a 2"x5" size) and they sand blast them. This gets rids of any surface contamination and gives the absolute best surface for adhesive to get a good purchase.

One other thing I will throw in because this comes up often. Gorilla Glue (is great glue) (or other Poly type expanding glue) foams up when activated with moisture. Guys will often say the foam fills cavities and it does but the foam has zero structural strength. You can scrape it away with your finger nail. This glue has to be at least partially compressed when it expands to gain strength. If a hidden tang knife is filled with Gorilla glue completely full, the resulting bond will hold exceptionally well and may outlast the steel and handle in toughness and life.
 
C Craft said:
Here is a tip I learned on another site sometime back. When doing a knife handle like this use those coffee stirrers that the they give at the fast food restaurants. They are usually small and thin and hollow like a straw. When pushed into the cavity you are trying to fill with epoxy it allows for the air to escape the mix via the coffee stirrer!
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Push it in after you pour, or put in 1st and then pull out? VERY INTERESTED!!!
 
Tracy said it best here - it's all about surface prep. Sand blasting is good. Since I don't have a sand blaster, the 36 grit is about best I can do to help provide that "bite" for mechanical bond - and that is MUCH more surface area for adhesion. Good rough surface, and CLEAN and degreased completely. Good epoxy will hold scales a LONG time, and with pins - a LONG LONG time.

Ken H>
 
Fatstrat said:
Push it in after you pour, or put in 1st and then pull out? VERY INTERESTED!!!
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Fill then push it in jig it up and down, it acts like vibrating concrete and also allows for the epoxy to have a way for the trapped air pockets to escape. That is why I never use 5 min, epoxy. Because even when you have everything ready to go, things do not always go as planned. 30min gives time to move and reposition as well allowing for a little more time for clean-up!
 
OK, so I remember glue wars and as I am reading this thread I have been wracking my brain about this revelation. I remember reading everything I could about the glue wars and the conclusions drawn because of it. However this thread and the comments on Devcon has caught my attention as I have not heard of the five year plus, failure factor!! :what!:

So what you are trying to say the glue self destructs after five years. I find this odd but, I have heard of have heard of stranger things. I would love to hear some more comments about this factor.

I know a well known maker that has been using it for years and as far as I know he has never had a failure! :les: He had one knife that stayed underwater in the mud after a hurricane and resulting flood for about month or more! He said the knife once cleaned up was as good as the day it was built and absolutely no problems with handle failure and it was a Devcon epoxy handle!

In my opinion the key to any epoxy getting a bite is preparation, which means everything needs to be as clean as possible and giving the epoxy some way to bite the metal, and the handle material, doesn't hurt at all. The maker I was speaking of uses holes drilled from side to side, and when possible into the handle material as well.

I do this same thing something I learned when I use to do furniture and custom cabinets. Wood glue will often dry out and fail with age. If you use epoxy and pocket the glue connection, well I have never had a call back for a failure using pockets drilled into joints.

When it comes to knife handle I usually do not rely on just one form of hold. I will pin the handle material as well, whenever I can, as well as drilling the handle material and the actual handle of the knife! You can't have too much redundancy when it comes to attaching a knife handle, IMO!!
 
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Well my glue up is done. To be honest, not quite sure if I did it right or of results quality. I used Devcon 30 minute epoxy because I had some I bought before I learned about the G-flex. Placed antler in padded vise, hole up. Heated the Devcon in a pan of water on stove, just shy of boiling. Mixed the entire amount of Devcon and poured the handle full. Sat the Devcon container down and picked up the straw. Looked back at the handle and it was no longer full. I don't know if an air bubble surfaced or it was absorbed into the antler morrow. So I sat the straw back down and reached for the Devcon. And was amazed to find that it was no longer liquid. But a large mass of jello that had expanded 100% above the container. And was getting hard. All this happened in less than two minutes. I scooped as much jello into the handle hole as I could before it started getting too hardened. And completely forgetting the straw put the tang in. The tang was always a tight fit, but now it was REAL tight. And only bottomed with much applied pressure. I figured with the already tight fit, that it wouldn't take much glue due to displacement by the tang. And expected glue overflow. But there was no overflow. Really don't know if displacement filled the handle cavity or not. And the glue was hardening so fast that I couldn't get the handle back out to check. So I had no choice but to just clamp it and let it dry. But it is now secure and looks good. But I have no idea if it is actually properly glued inside the handle.
 
I wondered about that warming advice. I've mixed epoxy before in a very cold shop and it took way longer to cure. I kind of thought heating it would just speed up the chemical reaction, sounds like it did. I glued my scales on too, Saturday, with 5 minute Loctite, tinted with a speck of India ink and it is nerve wracking on such a time crunch. I'll bet yours is ok, especially if you're going to put a pin in it too.
 
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bladegrinder said:
Actually these are just opinions, from different knife makers and their experience with different epoxies. I haven't seen any scientific stuff here on epoxies so there just opinions, just like mine. I have knives out there that I made twenty five years ago that show no delamination of the scales, and there not sitting in safes, there being used. sorry if I ruffled some feathers, but I'm in this for the long haul too, and I haven't had any of the problems that were mentioned here. so why should I change the way I do things ?
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Kindly read Ed's post's #4 and #19 where Ed learns from the scientist/Chemist that formulates many of these epoxies that have a planned life and will start to break down after only 1-2 years. When the start to break down and when failure can happen are to different things, but I will go with the 35 years of G/Flex epoxy since the one failure I had did happen at about 5 years was from ether the Devcon 2 ton or their 5 Minute.

I have used Gorilla glue at times. No failure problems but the foaming action can be a pain and I had to monitor the glued up knives for a hour or so to make sure no epoxy bubbled up into the front of the scales. I like to use Loveless style bolts because of the strength of the mechanical connection and then with G-Flex to seal and hold things together if their is any expansion or contraction of the stabilized woods I feel I am keeping any chances of handle problems on my culinary & hunting knives to a minimum.
 
Hey, just send that knife to me in Florida for 25 years of daily testing. I'll send it back at the end of the test period or when it fails. The knife looks good. Let's see some more.
 
Yeah, heat will make it cure faster. I think I mentioned that in an earlier post. If not, I meant to. But still, g-flex takes at least 3 hours to cure to the point that it can no longer be poured or scooped. Warming it to 90 or 100 F. will still give you about two hours to work with it.

Generally speaking, g flex cures to solid in about 3 hours, can be handled and moved in 7 hours, reaches full cure in 24 hours, and continues to harden to full strength over the next 2-3 days.
 
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